This study will prospectively examine the impact of a police education program (PEP) to align law enforcement and HIV prevention, since policing practices are key drivers of HIV among people who inject drugs (PWID) and sex workers. PEPs incorporating harm reduction have been successfully piloted in several countries but were limited to brief pre-post assessments; the impact of PEPs on policing behaviors and incidence of needle-stick injuries (NSIs) is unknown. Since police departments are unlikely to permanently adopt PEPs unless they are convinced that it will protect officers' health, we have partnered with the Tijuana police department who agreed to adopt our PEP into their training program. Our binational team will evaluate its efficacy through Proyecto Escudo (Project Shield) as follows: 1) To evaluate the efficacy of the PEP on uptake of occupational safety procedures, as assessed through the incidence of occupational NSIs (primary outcome). 2) To evaluate PEP efficacy on changes in secondary outcomes: i) knowledge of transmission, prevention and treatment of HIV and related infections; ii) attitudes towards PWID, sex workers and HIV-infected persons; iii) adverse behaviors that interfere with HIV prevention; iv) protective behaviors. 3) To assess potential mediating and moderating factors influencing PEP efficacy. We will conduct a modified stepped-wedge randomized controlled trial of the PEP involving all active duty police officers in Tijuana (N=2000). Police mandated for periodic refresher training will be randomly assigned to classes of 20 to receive one 3-hour PEP course over 2 years until the entire force is trained. NSI incidence and geocoded arrest data will be assessed department-wide (Aim 1). A sub-cohort sample (5 per class, N=500) will be invited to undergo pre- and post-PEP surveys with semi-annual follow-up for 2 years to assess self-reported NSIs (Aim 1), attitudinal and behavior changes (Aim 2) and mediators/moderators (Aim 3). The PEP's impact on PWIDs will be externally validated through a parallel cohort of Tijuana PWIDs followed through 2020 under separate funding. This is the first trial to assess efficacy of a PEP on policing behaviors that place PWID and police at elevated risk of HIV and blood-borne infections. Our study is responsive to a Global Commission on Drug Policy report which condemns policing behaviors that fuel blood-borne infections based on extensive international evidence. Findings are expected to help bring PEPs to scale in the growing number of countries where policing is a documented driver of HIV acquisition.